Field conditions for ion excitation in linear ion processing apparatus

Abstract

Methods for applying an RF field in a two-dimensional electrode structure include applying RF voltages to main electrodes and to compensation electrodes. The voltages on the compensation electrodes may be proportional to the voltages on the main electrodes so as to optimize the RF field for processes involving ion excitation, including collision-induced dissociation. Electrode structures may include main trapping electrodes, one or more compensation electrodes, one or more ion exit apertures, and a device or circuitry for applying the various desired voltages.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is related to the following co-pending U.S. patent applications, which are commonly assigned to the assignee of the present disclosure: “Two-Dimensional Electrode Constructions for Ion Processing,”“Compensating for Field Imperfections in Linear Ion Processing Apparatus,”“Adjusting Field Conditions in Linear Ion Processing Apparatus for Different Modes of Operation,” and “Rotating Excitation Field in Linear Ion Processing Apparatus.” each of which is being filed concurrently with the present application on Jan. 30, 2006.FIELD OF THE INVENTION [0002] The present invention relates generally to the manipulation or processing of ions in electrode arrangements of two-dimensional or linear geometry. More specifically, the invention relates to methods and apparatus for improving field conditions in such electrode arrangements for processes related to ion excitation such as collision-induced dissociation (CID). The methods and a...

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Benefits of technology

[0015] According to other implementations, the electrode structure may have one or more compensation electrodes. One or more of the main electrodes may have apertures. The number of compensation electrodes may be less than or equal to the number of apertures. The RF voltages applied to the one or more main electrodes may also be applied to the one or more compensation electrodes at an amplitude that are the same or different than the amplitude of the voltage on the one or more mai

Problems solved by technology

The inherently generated fields may or may not be intentional and, depending on the mode of operation, may or may not be desirable or optimal.

In practice, however, the electrodes include a number of different features that engender various types of symmetrical and/or asymmetrical field faults or distortions affecting the manipulation and behavior of ions.

The slot is a significant source of field faults that may be considered detrimental to the ion ejection or mass scanning process.

In a real quadrupolar RF field employed for trapping ions, such imperfections may adversely affect the ion ejection process by causing shifts in the ion ejection time that are dependent on the chemical structure of the ions.

It is has been observed by the present inventor, however,

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